NAME

ng_iface — interface netgraph node type

SYNOPSIS

#include<netgraph/ng_iface.h>

DESCRIPTION

An iface node is both a netgraph node and a system networking interface. When an iface node
is created, a new interface appears which is accessible via ifconfig(8). Iface node
interfaces are named ng0, ng1, etc. When a node is shutdown, the corresponding interface is
removed and the interface name becomes available for reuse by future iface nodes; new nodes
always take the first unused interface. The node itself is assigned the same name as its
interface, unless the name already exists, in which case the node remains unnamed.
An iface node has a single hook corresponding to each supported protocol. Packets
transmitted via the interface flow out the corresponding protocol-specific hook. Similarly,
packets received on a hook appear on the interface as packets received into the
corresponding protocol stack. The currently supported protocols are IP, IPv6, AppleTalk,
IPX, ATM, NATM, and NS.
An iface node can be configured as a point-to-point interface or a broadcast interface. The
configuration can only be changed when the interface is down. The default mode is point-to-
point.
Iface nodes support the Berkeley Packet Filter (BPF).

HOOKS

This node type supports the following hooks:
inet Transmission and reception of IP packets.
inet6 Transmission and reception of IPv6 packets.
atalk Transmission and reception of AppleTalk packets.
ipx Transmission and reception of IPX packets.
atm Transmission and reception of ATM packets.
natm Transmission and reception of NATM packets.
ns Transmission and reception of NS packets.

CONTROLMESSAGES

This node type supports the generic control messages, plus the following:
NGM_IFACE_GET_IFNAME (getifname)
Returns the name of the associated interface as a NUL-terminated ASCII string.
Normally this is the same as the name of the node.
NGM_IFACE_GET_IFINDEX (getifindex)
Returns the global index of the associated interface as a 32 bit integer.
NGM_IFACE_POINT2POINT (point2point)
Set the interface to point-to-point mode. The interface must not currently be up.
NGM_IFACE_BROADCAST (broadcast)
Set the interface to broadcast mode. The interface must not currently be up.
NGM_CISCO_GET_IPADDR (getipaddr)
This message is defined by the ng_cisco(4) node type; see ng_cisco(4) for a
description.

SHUTDOWN

This node shuts down upon receipt of a NGM_SHUTDOWN control message. The associated
interface is removed and becomes available for use by future iface nodes.
Unlike most other node types, an iface node does not go away when all hooks have been
disconnected; rather, and explicit NGM_SHUTDOWN control message is required.

ALTQSupport

The ng_iface interface supports ALTQ bandwidth management feature. However, ng_iface is a
special case, since it is not a physical interface with limited bandwidth. One should not
turn ALTQ on ng_iface if the latter corresponds to some tunneled connection, e.g. PPPoE or
PPTP. In this case, ALTQ should be configured on the interface that is used to transmit the
encapsulated packets. In case when your graph ends up with some kind of serial line, either
synchronous or modem, the ng_iface is the right place to turn ALTQ on.